GDR -- list of things to do.

1. Make it possible to use menu and do the move command with a one-button
   mouse (add another item for MENU to the panel).  [done 2005/03/25]
2. Display keyboard shortcuts in the menu.          [done 2005/03/27]
3. Implement strong components algorithm.           [done 2005/03/26]
4. Update documentation.
5. Ask for confirmation in case of EXIT or CLEAR or READ.
6. Fix boolean type so that it works with 1999 standard and is portable.
